Field of the Application
The application generally relates to management of connection and resource, and more particularly, to apparatuses and methods for User Equipment (UE)-initiated connection release and resource release.
Description of the Related Art
Due to the growing demand for ubiquitous computing and networking, various cellular technologies have recently been developed, including the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, Time-Division LTE (TD-LTE) technology, and LTE-Advanced (LTE-A) technology, etc.
According to release 12 of the 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 36.331, only the Evolved-Universal Terrestrial Radio Access Network (E-UTRAN) can initiate the Radio Resource Control (RRC) connection release procedure which triggers the UE to release the RRC connection, including established radio bearers and all radio resources. That is, the UE can only passively wait for the E-UTRAN to release the RRC connection when the UE is configured to operate in the RRC_CONNECTED mode. Furthermore, according to release 12 of the 3GPP TS 36.413 and 36.418, the E-UTRAN may start a user inactivity timer when detecting that no data traffic associated with the UE is ongoing, and then initiate the RRC connection release procedure when the user inactivity timer expires. However, the value of the user inactivity timer may be too long, causing the UE to stay in the RRC13 CONNECTED mode with no data traffic ongoing. This is an unfavorable situation since the UE consumes more power in the RRC_CONNECTED mode. Not to mention that the UE will take up radio resources assigned by the E-UTRAN but not use them, which results in poor utilization of radio resources.
In order to meet the demand for higher data rates in wireless communications, support for wider transmission bandwidths is required, and the so-called Carrier Aggregation (CA) and Dual Connectivity (DC) techniques have been proposed to allow for the expansion of effective bandwidths delivered to a UE. Using the CA technique, more than 2 carriers may be aggregated to form a larger transmission/reception bandwidth. Each of the aggregated frequency channels is generally referred to as a component carrier, which may be taken as a component of the aggregated bandwidth. Using the DC technique, a UE may perform data transceiving simultaneously with two base stations, e.g., a macro base station and a micro base station.
According to release 12 of the 3GPP TS 36.331, the CA or DC functionality may only be configured by the service network. Specifically, the service network configures the UE to perform measurements on Secondary Cell (SCell) frequencies and to report the measurement results. If the measurement results indicate that the signal quality of an SCell is good enough, the service network will configure the UE to add the SCell. Otherwise, if the measurement results indicate that the signal quality of an SCell becomes too bad, the service network will configure the UE to delete the SCell. That is, the UE can only passively wait for the service network to configure the CA or DC functionality. However, there may be situations where the CA or DC functionality is not desired to be configured to the UE, due to the CA or DC functionality consuming more power and causing the operating temperature to rise.